It is commonly well known that shoulder firearms, such as rifles and shotguns, recoil suddenly and violently in a rearward direction when the firearm is discharged. The amount of resulting force that is felt by the shooter is jarring and is often uncomfortable, and to that end there have been numerous attempts that have been made in the field to devise a recoil reducing apparatus in an effort to dissipate the recoil force, rather than to have the shooter receive a sharp blow to the shoulder.
The types of recoil reducing apparatus that are presently known have included numerous mechanical and/or pneumatic systems and hydraulic type devices. For example, Ahearn, U.S. Pat. No. 3,233,354, relates to a class of hydraulic-type recoil reducing apparatus. According to the Ahearn patent, a recoil apparatus interconnects the butt portion (the portion of the stock which engages the shoulder of the shooter) and the forepiece of the stock. This apparatus includes a hydraulic cylinder and piston which axially reciprocates so as to permit hydraulic fluid contained in the cylinder to escape about the piston in order to permit relative movement between the two portions of the stock in a controlled manner and in which the recoil force is absorbed by the motion of the piston through the fluid.
A fundamental problem found in hydraulic type recoil reducing apparatus, such as described by Ahearn, is their insensitivity to certain factors, such as the type of ammunition used and the weight of the firearm itself. For example, a selection of different types of ammunition will often be commercially available for a particular caliber or gauge of the firearm, meaning that the shooter is free to select the ammunition most suited to his or her application. In addition, the shooter may select a particular type of ammunition in order to obtain particular ballistics or firing characteristics. Each of the preceding factors contribute to the recoil characteristics of the firearm and therefore may limit the effectiveness of the recoil reducer apparatus.
Therefore, attempts have been made in an effort to provide adjustability in such apparatus. U.S. Pat. No. 4,439,943 to Brakhage is an example of a recoil reducer apparatus that provides adjustability. In brief, this rather complex apparatus includes a pair of pistons, namely a primary piston and a secondary piston, which are provided within a hydraulic cylinder. A piston rod extends through the secondary piston and partially into the main piston through an aperture. The aperture according to this disclosure is frusto-conical to permit the attachment of a frusto-conical piston rod end. The pistons are supported to prevent rotation and a passage is formed between the frusto-conical portion of the aperture and one side of the main piston to permit fluid to pass therethrough during recoil. The secondary piston which is sealed to prevent fluid leakage provides a biasing force to return the apparatus (i.e., the main piston) to a neutral position. Turning of the piston rod changes the characteristics of the passage and therefore changes the damping characteristics of the apparatus as fluid passes through the piston when the firearm is discharged.
Other forms of recoil reducing apparatus include pads that are added to the shoulder firearm, the pads being at least partially defined by an elastomeric material. These devices, however, are able to provide only a fractional amount of energy absorption and are therefore only moderately effective.